Currently, in order to save cost of a discharge circuit of a battery, a two-wire discharge circuit of the battery in which neutral-wire connection of the battery is not required is proposed in the industry on the basis of a three-wire connection discharge circuit such as the Vienna (Vienna) circuit or the similar-Vienna circuit. As shown in FIG. 1, which is a schematic structural diagram of the two-wire discharge circuit of the battery, the two-wire discharge circuit of the battery may include: a supply power (that is, battery); a positive-bus capacitor C1 and a negative-bus capacitor C2 which are connected to a system neutral point N; three first discharge branches, a terminal of each of the first discharge branches is connected to a positive terminal (Bat+) of the battery, and the other terminal is connected to a system neutral point N; and three second discharge branches, a terminal of each of the second discharge branches is connected to a negative terminal (Bat−) of the battery, and the other terminal is connected to the system neutral point N.
Each of the first discharge branches may include a first thyristor, a first inductor L1, a first switch transistor T1, a first freewheeling diode D1 and a first diode which is connected to the first switch transistor T1 in parallel. In each of the first discharge branches, an anode of the first thyristor is connected to the positive electrode of the battery, a cathode of the first thyristor is connected to a first terminal of the first inductor L1, a second terminal (which is not connected to the first thyristor) of the first inductor L1 is connected to a collector of the first switch transistor T1, an emitter of the first switch transistor T1 is connected to the system neutral point N, an anode of the first freewheeling diode D1 is connected to the second terminal of the first inductor L1, a cathode of the first freewheeling diode D1 is connected to a non-system neutral point of the positive-bus capacitor C1, an anode of the first diode is connected to the emitter of the first switch transistor T1, and a cathode of the first diode is connected to the collector of the first diode T1. It should be further illustrated that, the two-wire discharge circuit of the battery may include three first discharge branches corresponding to three phases A, B and C respectively. Also, for ease of distinguishing, in FIG. 1, the first inductor L1, the first switch transistor T1, the first freewheeling diode D1 and other electronic elements in the first discharge branch corresponding to phase A may be denoted as LA1, TA1, DA1 and the like respectively; the first inductor L1, the first switch transistor T1, the first freewheeling diode D1 and other electronic elements in the first discharge branch corresponding to phase B may be denoted as LB1, TB1, DB1 and the like respectively; and the first inductor L1, the first switch transistor T1, the first freewheeling diode D1 and other electronic elements in the first discharge branch corresponding to phase C may be denoted as LC1, TC1, DC1 and the like respectively, which are not described repeatedly in the present disclosure.
Similarly, each of the second discharge branches may include a second thyristor, a second inductor L2, a second switch transistor T2, a second freewheeling diode D2 and a second diode which is connected to the second switch transistor T2 in parallel. In each of the second discharge branches, a cathode of the second thyristor is connected to the negative electrode of the battery, an anode of the first thyristor is connected to a first terminal of the second inductor L2, a second terminal (which is not connected to the second thyristor) of the second inductor L2 is connected to an emitter of the second switch transistor T2, a collector of the second switch transistor T2 is connected to the system neutral point N, a cathode of the second freewheeling diode D2 is connected to the second terminal of the second inductor L2, and an anode of the second freewheeling diode D2 is connected to a non-system neutral point of the negative-bus capacitor C2, and an anode of the second diode is connected to the emitter of the second switch transistor T2, and a cathode of the second diode is connected to the collector of the second switch transistor T2. It should be illustrated that, the two-wire discharge circuit of the battery may include three second discharge branches corresponding to three phases A, B and C. Also, for ease of distinguishing, in FIG. 1, the second inductor L2, the second switch transistor T2, the second freewheeling diode D2 and other electronic elements in the second discharge branch corresponding to phase A may be denoted as LA2, TA2, DA2 and the like respectively; the second inductor L2, the second switch transistor T2, the second freewheeling diode D2 and other electronic elements in the second discharge branch corresponding to phase B may be denoted as LB2, TB2, DB2 and the like respectively; and the second inductor L2, the second switch transistor T2, the second freewheeling diode D2 and other electronic elements in the second discharge branch corresponding to phase C may be denoted as LC2, TC2, DC2 and the like respectively, which are not described repeatedly in the present disclosure.
It also should be illustrated that, the inductor shown in FIG. 1 may refer to a PFC (Power Factor Correction) inductor, which is not described repeatedly in the present disclosure.
With the two-wire discharge circuit of the battery shown in FIG. 1, a Boost (boost) function can be realized without the neutral-wire connection of the battery. For example, taking phase A as an example, two PFC inductors, two switch transistors, two freewheeling diodes and the like in corresponding the first discharge branches and the second discharge branches can operate with the positive-bus capacitor and the negative-bus capacitor as a whole in an ideal situation. The battery can store energy by the PFC inductors when the switch transistors are turned on, and the battery and the PFC inductors can charge the bus capacitors via the freewheeling capacitors when the switch transistors are turned off, to realize the boost function. Also, in a case of three-phase control, the three phases may be interleaved by 120 degrees, therefore, current ripples of the battery are reduced greatly, and circuit performance is improved.
In practice, however, the two-wire discharge circuit of the battery is unable to operate in an ideal mode, since various factors may have adverse effects on the two-wire discharge circuit of the battery. For example, in a case that the switch transistors in the circuit have different action delays, a problem of bus voltage unbalance may occur, which results in abnormal operation of the circuit, and affecting operation performance of the circuit. Therefore, it is urgent to provide a circuit control solution for the two-wire discharge circuit of the battery, to solve the above problems.